Extraction of uranium



, 2,897,045 Patented July 28, 1959 EXTRACTION F URANIUM Robert D. Kesler and David D. Rabb, Columbus, Ohio,

assignors to the United States of America as represented by the United States Atomic Energy Commission No Drawing. Application February 6, 1950 Serial No. 142,704

8 Claims. (Cl. 23-145) This invention deals with the extraction of uranium values, and in particular with the extraction of uranium from roasted ores, specifically from salt-roasted ores of the carnotite type.

Carnotite-type ores contain uranium and vanadium both of which are usually recovered by leaching the ore with an aqueous solution after roasting. A solution of sodium carbonate has been preferred for the leaching process. Prior to the leaching step, the ore is admixed with sodium chloride and roasted. While this salt-roasting process converts the vanadium into a form in which it is readily complexed by sodium carbonate and its extraction is facilitated, the solubility and consequently the extractability of uranium is unfavorably afiected by salt-roasting.

In order to overcome this drawback, a great manyexperiments have been carried out by the inventors to study the effect of the various ingredients of carnotite ores and also of various additives on the extractibility of uranium.

It is an object of this invention to provide a process for treating carnotite-type ores by which the solubility of uranium, in particular in sodium carbonate solutions, is improved.

For the study, a synthetic uranium ore was prepared which was free from most of the secondary ingredients encountered in naturally occurring carnotite; it consisted of a mixture of 100 g. of silica sand and 0.32 g. of sodium uranyl carbonate, N21 UO (CO This synthetic ore, when leached with an aqueous solution of sodium carbonate, yielded a 100% extraction of the uranium present. However, when the ore was mixed with 10% by weight of sodium chloride and roasted at 1560 F. for thirty minutes with 0.12 c.f.m. of air, the uranium extraction with sodium ,carbonate solution was reduced to 19%.

The eifect on the uranium solubility of the individual components occurring in carnotite ores and/or of various additives was then investigated. For this purpose, the same synthetic uranium ore as set forth above was admixed with the ingredients to be tested in various quantities, roasted and then extracted with a sodium carbonate solution. The effect of the following additives was examined: CaO, MgO, A1 0 Fe O CaF Na P0 FeS, V 0 iron, coke, and Na CO While CaO, MgO, A1 0 Fe O and CaF were found to be detrimental because the uranium solubility was reduced by their presence, iron, coke, and Na CO (in amounts of 1 to 5%) were found to have no appreciable effect on the uranium solubility.

Favorable effects, however, were obtained with Na- PO pyrite, sulfur dioxide, phosphorus pentoxide, and in particular with vanadium pentoxide. In the following table the results obtained with these substances are compiled. For the experiments listed there the synthetic ore was mixed with 10% sodium chloride and the additive shown in the table in the quantity listed there, and the mixture was then roasted for thirty minutes at 1560 F. Thereafter, the roasted ore was leached with an aqueous solution of sodium carbonate and the quantity of uranium extracted was determined therein.

Table I Percent U Quantity of additive, extracted Type 01' additive percent by weight of with ore Na COa solution n Naaroia g3 Pyrite .i S02- 92 Pzos- 74 V205 6g This table shows that the best results are obtained with vanadium oxide, and this substance was studied further. It was found that less than 0.2% of V 0 did not yield any improvement and that the minimum quantity of V 0 required in order to obtain a complete uranium extraction is 5% by weight V 0 per 1% by weight of uranium. This proportion was found to hold true for concentrations of uranium in the synthetic ore of 0.16 and 0.32%, while, for instance, with a uranium content of 0.64% the minimum quantity for complete uranium extraction was 6% by weight of vanadium oxide per 1% by weight of uranium.

The experiments were then repeated with natural carnotite ores. The ore was crushed prior to roasting. While a better extraction is obtained with a finer particle size, a coarser ore was more advantageous in order to avoid dust formation during roasting. For this reason, the 10 to 20 mesh size was found to be most advantageous.

Vanadium pentoxide had to be added prior to salt roasting in a. quantity sufficient to combine any free calcium oxide present as calcium metavanadate and also suflicient to obtain the minimum V O -to-uranium ratio of 5:1 for complete uranium extraction. This is necessary because otherwise the free calcium oxide reacts with the vanadium oxide and the quantity is thus reduced below that required for optimum efliciency. It

was found that the percentage of vanadium oxide should be 3.2 times the percentage of free calcium oxide; the formula for the minimum quantity required therefore is: Percent V O 32 percent CaO-l-Sxpercent U.

The analyses of four carnotite ores including a dolomitic shale type of ore are given in the following table.

Table II Analyses, percent Source of ore U V105 s10, &0 Fe Oi 441,0, F, MgO S NaiO K,o P 05 T;

WildSteermine 0. 34 3.40 86.16 0.79 .71 4.0 .01 1.4 .094 Gyp Valley 0.57 2.88 78.77 2.54 1.19 4.0 .02 1.4 .034 0.1 1.0 Radium7 0. s4 2. 50 81.3 3.40 2.12 5.1 .1 0.24 0.75 0.03 0.12 Bald Eagle 0.72 2.60 17.6 10.5 .052

1 Dolomitic shale type of earnotite ore. The re ults obtained with and without the addition of instance, the free calcium oxide present in the carnotite vanadium oxide when the salt-roasted (1-560 F. for thirty ore may also be tied up as the phosphate, the sulfate or minutes) ores of Table II were leached with a sodium the fluoride instead of as the metavanadate. carbonate solution are given in the'following table. It What is claimed is: is obvious from this table thatvanadium-oxide has a 1. A process for extracting uranium from carnotite veryfavorable elfect on the extractability of uranuim. ores, comprising adding about 10% of Sodium Ch oride Table I" and adding at least 5% by weight of vanadium pentoxide per 1% by weight of uranium to'thev ore, roasting the mixture thus obtained and leaching the roasted mass with an ggffg gf'. U fi? aqueous solution'of alkali'carbonate.

cent of ore percent 2. The process of claim 1 wherein the alkali carbonate welght is sodium carbonate.

3. The process of claim 1 wherein about 6% by weight Wild Steer 3 23 of vanadium pentoxide per 1% by weight of uranium is Gyp Valley.-. 0 50 used.

3' $3 14. [Fhe-processof claim l wheremroastmg is earned Radium 7 7.0 83 outatabout 1600" .F. for thirtyt'rninutes. Bald Eagle 9 f 5. The process of claim 4 wherein theroasting-is-carriedgout-at 1560" 1F. for thirtyminutes.

Similar experiments were carried out with Pyrite 6. Theprocess of claim l whereinthe alkali carbonate While with the synthetic ore pyrite was found to have an t g concentrauon rangmg from 3 improving'eflect on the solubility withquantities as. low o f t f am fit as 1.5%, the amountnecessary for improving uranium i f m c h e extraction from natural 'carnotite was found to range orfsfiompnsmgaddmgfrom sodlum londe from 12 to 16%, depending upon the type of ore. This to attic i' f selectedfmm. the group isprobably due to'the formation of'uranous sulfate. conslstmg-oflvanadmm h oxide" Sulfate The quantities of sodium chloride are not critical, but 40 and"fluor.lde quanmyi'spfficlent-to p an'Qflthe an amount of'from 6 to 10% of the ore was found to i i ad mgvanadmmbe best suitable. Roasting with dry air was found 'to pentoxlde m 7a gummy to 01.3mm of at least i give better results than with air containing a considerable f zf bx gz ggig giz g g z $311552: amount of moisture. The best roasting temperature was o Hg r hi d around 1600 F.,1560 F. being'the optimum. The roast- 4.5 1560 mmutes and 16.210 13g waste ing time is preferably not in excess of thirty minutes Iranass withia 3-to-9% aqueous solut1on-of .sodulm carte The quantity of 'all should be sufliclent to irnaintalnan ona oxidizing atmosphere foroptimum results; inthefore- F i i' i i g g i going experiments, from O.l2-to 0.2-4c.f.m. was-found g i m 92 0 S suitable. Extraction With the sodium carbonate solution 2233 2 53 1 3 f gg sz a gfi g 3 23 3 is preferably carried out during agitationof themixture. cabin; oxide of vanadium The concentration of-sodium carbonate solution giving p p h b P the best resultswas between -3 and 9%. A-quantityof a $83 335 gg j g g f g fig g 4 parts of sodium carbonate solution and one part of a 3 t u t lution of i solids, althoughnot critical,'has beenfound preferable. ig 'g g 0 6 so Wide ranges of temperatures for the leaching solutionare a e g suitable the rangehbetweenbsoo theiboging g References Cited inthe file of this. patent bein referred t e ve estresu ts were 0 talne at aboft 3 Q ry UNITED -STATES PATENTS It will ibeunderstood thatthis invention is nottobe 0 1,049,145 Rzidclifi, Dec. 31, 1912 limited to the details given herein but that it may 'be 2,217,665 Brown Oct. 15, 1940 modified within the scope ofthe appended claims. For 2,471,345 Nye etal. May 24, 1949 

1. A PROCESS FOR EXTRACTING URANIUM FROM CARNOTITE ORES, COMPRISING ADDING ABOUT 10% OF SODIUM CHLORIDE AND ADDING AT LEAST 5% BY WEIGHT OFVANADIUM PENTOXIDE PER 1% BY WEIGHT OF URANIUM TO THE ORE, ROASTING THE MIXTURE THUS OBTAINED AND LEACHING THE ROASTED MASS WITH AN AQUEOUS SOLUTION OF ALKALI CARBONATE. 